The natural crystalline lens of the eye plays a primary role in focusing light onto the retina for proper vision. However, the lens can become damaged due to injury or become cloudy because of aging or disease and form a cataract. To restore vision to the eye, the natural lens must be surgically removed and an artificial lens implanted as a replacement.
Many surgical procedures have been developed for removing the natural lens. The use of small incision techniques tends to cause less trauma and fewer operative and post-operative complications. According to these procedures, a slender tool is inserted through a small incision made in the eye and into the natural lens. The distal tip of the tool functions to fragment the lens and then aspirate the lens material out of the eye through an internal duct. In one process, disclosed in U.S. Pat. No. 5,222,959, the tip is rotated to cut the lens into small pieces without damaging the capsular bag. In another process, known as phacoemulsification, the tip is subjected to ultrasonic vibrations to emulsify the lens. Alternatively, the tip may be an ultrasonically assisted rotary tip which cuts the lens by longitudinal and rotational motion.
Surgical devices for performing such operations are typically hand-manipulatable and comprise a housing, a central shaft, and a cutting or polishing tip. A plurality of tips can be interchangeably mounted onto the distal end of the shaft. The tips each include a working end for performing the cutting or polishing and a mounting end having a threaded shank. The shank is screwed into a threaded bore formed in the end of the shaft.
As can be appreciated, the tip must be securely attached to the shaft during the operation. To effect a tight connection, flats are provided on both the tip and the shaft to facilitate the engagement of each with a wrench. In one construction, a pair of opposite flats are formed on the tip adjacent the threaded shank, and a hexagonal nut segment is formed on the proximal end of the shaft which extends rearwardly beyond the housing. Accordingly, a pair of wrenches are used to tighten or loosen the tip onto the shaft. This is a cumbersome procedure which requires the user to manipulate a wrench in each hand as well as support and stabilize the tool.